Intragranular formation of austenite during delta ferrite decomposition in a duplex stainless steel

Evaluation of microstructure and texture across the welded interface of super duplex stainless steel and high strength low alloy steel

“…8, although the austenite daughter phase did not exhibit an ideal K-S or N-W OR, its OR with respect to the parent ferrite was very close to K-S in both layers. The partial satisfaction of OR models by the austenite was, on one hand, due to the presence of different morphologies of austenite across the cladding and on the other hand, due to the inherent partial satisfaction of the K-S or N-W ORs by the predominant WA needles and IGA particles [38,57,58].…”

Orientation relationships of intragranular austenite in duplex stainless steel weld metals

“…6 Secondary austenite with a Widmansta ¨tten-like morphology is generally also reported to be close to a KS or NW OR with the ferrite. 6,9,[14][15][16][17] These ORs have been seen also for intragranular austenite found after rapid cooling without reheating. 15,17 Intragranular austenite is often associated with the presence of hexagonal Cr 2 N precipitates.…”

“…6,9,[14][15][16][17] These ORs have been seen also for intragranular austenite found after rapid cooling without reheating. 15,17 Intragranular austenite is often associated with the presence of hexagonal Cr 2 N precipitates. The nitrides form below approximately 900-950uC during isothermal treatment or during fast cooling due to supersaturation of N in the ferrite.…”

“…Austenite in duplex weld metals tend to have an OR relative to the adjacent ferrite that is close to either NW or KS. 6,9,[12][13][14][15][16][17] These two ORs differ only by a relative rotation of 5?26u about the normal of the parallel close packed planes of the two phases. Furthermore, the exact KS and NW orientations are unlikely to exist, but tend to be irrational with small angles between the close packed planes.…”

“…It is commonly observed that secondary austenite forms with an OR close to KS or NW with the ferrite. 6,9,[14][15][16][17] Nitrogen solubility of ferrite fall rapidly with decreasing temperature, and Cr 2 N can start to form at about 900-950uC. It has been suggested that nitrides might act as nucleation sites for intragranular austenite.…”